1. Field of the Invention
The present invention relates in general to a phorometric apparatus and more particularly to an apparatus for producting a signal for timing for operations such as initiation, termination etc. in photometric measurement.
2. Description of the Prior Art
In general, in an automatic sample analysis apparatus or the like e.g. for colorimetrically analyzing successively a series of samples contained in a corresponding number of container cells, the sample container cells are held stationarily, while a light source and a photo-detector are moved relative to the stationary cells. Alternatively, the light source and the detector are positioned fixedly, while the sample cells are moved relative to the source lamp and the detector. Such relative movement is effected either continuously or intermittently. In any cases, it is necessary to produce signals for timing the measuring operations in synchronization with the initiation and the termination of the measurement for every sample cell as the cell assembly is displaced.
Hithertofore, it is known that a plate perforated with holes at positions corresponding to those of the sample cells is interposed between a small source lamp and a photo-transistor to thereby produce the timing signals synchronously with the initiation and the termination of the measurement for each cell. According to this known method, the position of the sample cell to be measured is at first detected and subsequently light transmitted through the cell is separately measured. The prior known method is disadvantageous in that the arrangement for producting the timing signals is complicated due to the fact that markings such as impresses have to be formed in the cells and/or switches must be employed for the detection of the cell position in case of a mechanical detecting system, while in the photoelectric detecting system an additional light source and a photo-detector are required for identifying or detecting the position of the sample cell to be measured. Nevertheless, reliability in operation can not be assured or a troublesome calibration or adjustment is required in case an accurate synchronization between the generation of the timing signals and the photometric measurement operations of the sample.